1. Field of the Invention
The invention relates to a radiological imaging apparatus, and more particularly, to a method for processing 3-dimensional (3D) distribution image of radiation source to acquire 3D distribution of radiological image with improved sensitivity and image resolution, and a system using the same.
2. Description of the Related Art
The invention relates to a position sensitive detector-based imaging apparatus which acquires a three dimensional (3D) distribution image of a radiation source existing within a living organism. The single-photon emission computed tomography (SPECT) and positron emission tomography (PET) are the two representative examples of a conventional radiological imaging apparatus. SPECT uses a mechanical collimator which is made from materials such as lead or tungsten to acquire image from the radiation source.
However, the gamma ray sensitivity and the image resolution are in inverse relationship with each other, according to the aperture size of the collimator.
That is, if the sensitivity increases, the resolution degrades, and if the resolution improves, then the sensitivity decreases. There also is a drawback related to the use of mechanical collimator. That is, SPECT imaging equipment has increased size to accommodate the mechanical collimator, and has to be rotated to acquire 3D image.
PET concurrently receives 511 keV gamma rays emanating from the radiation source to acquire images of the radiation source distributed within the matter. Unlike SPECT, PET does not have to be rotated due to the circular arrangement of detectors. However, since PET uses higher magnitude of gamma ray energy than SPECT, PET has more Compton scattering due to photoelectric effect of the gamma rays at the detectors, rather than the entire energy is absorbed.
Due to the multi-scattering of gamma rays inside the respective detectors, the gamma rays are measured concurrently through a plurality of channels. Since the radiation source is not always present at the center of the imaging apparatus, the gamma rays can enter the apparatus through not only the surface of incidence, but also the side of the apparatus.
However, the above causes inaccuracy of position measurement. Such event works as a background event that obscures the image of the imaging apparatus such as PET. Due to the above-mentioned limits, the conventional imaging apparatus including PET has image resolution which is limited within a range of several mm at the maximum.